Blanchard, a 29-year-old IBM employee from Bromont, Quebec, was suffering from depression and took time away from work, relying on sick-leave benefits from her insurer, Manulife Financial.

The monthly payments were suddenly halted. When she called Manulife to ask why, she says she was told that it had espied photos on her Facebook page that showed her cheerful. Ergo, the argument allegedly went, she was able to work. Which led to the second ergo: no more payments.

A group of Venezuelan students were recently arrested by local police for various theft charges. After further investigation, authorities proved that they were using many social networking sites, especially Facebook, to monitor their victims' activity and rob their houses while out of town.